Automatic Detection and Correction of Random Telegraph Signal Artifacts in Earth Observation Images

Satellite optical and infrared images can be degraded by a piecewise-constant random artifact called random telegraph signal (RTS), which is caused by unstable semiconductor defects in the photodetector. In this letter, we aim at proposing new techniques to detect and correct such artifacts in the specific context of push-broom detectors, where some columns exhibit RTS that superimposes with the landscape. Our detector is based on a nonparametric statistical test that compares the distribution of each column to its neighbors. Concerning the RTS correction, we first propose a signal processing method that estimates the levels and jumps of the RTS. Then, we propose another method inspired by variational image destriping, which directly estimates the RTS through the use of total variation (TV). Experiments—on Pléiades images with synthetic RTS and on a real SPOT-5 image—show the effectiveness of the proposed techniques

RTS effect detection in Sentinel-4 data

The future ESA Earth Observation Sentinel-4/UVN is a high resolution spectrometer intended to fly on board a Meteosat Third Generation Sounder (MTG-S) platform, placed in a geostationary orbit. The main objective of this optical mission is to continuously monitor the air quality over Europe in near-real time. The Sentinel-4/UVN instrument operates in three wavelength bands: Ultraviolet (UV: 305-400 nm), Visible (VIS: 400- 500 nm) and Near-infrared (NIR: 750-775 nm). Two dedicated CCD detector have been developed to be used in the Focal Plane Subsystems (FPS), one for the combined UV and VIS band, the other covering the NIR band. Being a high resolution spectrometer with challenging radiometric accuracy requirements, both on spectral and spatial dimensions, an effect such the Random Telegraph Signal (RTS) can represent a relevant contribution for the complete system accuracy. In this work we analyze the RTS effect on data acquired during the FPS testing campaign with qualification models for the Sentinel-4/UVN detectors. This test campaign has been performed in late 2016. The strategy for the impact assessment of RTS is to measure the effect at room temperature and then to extrapolate the results to the at instrument operational temperature. This way, very-long lasting data acquisitions could be avoided since the RTS frequency is much lower at cryogenic temperatures. A reliable technique for RTS effect detection has been developed in order to characterize the signal levels amplitude and occurrence frequencies (flipping rate). We demonstrate the residual impact of the RTS on the global In-Orbit Sentinel-4/UVN instrument performance and products accuracy